The alveoli are lined with mucus and are surrounded by a network of blood capillaries. They have very thin walls for gases to be absorbed through. An individual air sac is called an alveolus. The layer of moisture in the alveoli allows gases to dissolve so that they can diffuse quickly.
Discontinuous variable ;)
Answer:
a series of pools built like steps to enable fish to bypass a dam or waterfall.
Explanation:
A fish ladder, also known as a fishway, fish pass or fish steps, is a structure on or around artificial and natural barriers to facilitate diadromous fishes' natural migration.
<span> A. a process by which organism keep internal conditions relatively constant despite changes in external conditions. </span>
